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NIOS Class 12 Biology Chapter 9 Nutrition in Plants – Mineral Nutrition
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Nutrition in Plants – Mineral Nutrition
Chapter: 9
MODULE – II: FORM AND FUNCTION OF PLANTS AND ANIMALS
NIOS TEXTBOOK QUESTIONS ANSWERS
INTEXT QUESTIONS 9.1
1. What are nutrients?
Ans. They are chemical substances in food of plants.
2. Define aeroponics.
Ans. The aeroponics is defined “as a technique of growing the plants in an air or mist environment without using soil.”
3. Why is it necessary to aerate nutrient solution in water culture?
Ans. To supply O2 in energy quantity.
INTEXT QUESTIONS 9.2
1. In which form do plants get oxygen?
Ans: Molecular form from the water or air.
2. Molybdenum is a micronutrient. Give reason.
Ans. It is required by the plant in very small amount app. 0.1 mg per gram of the dry matter or even less of it.
3. Why are carbon, oxygen, potassium and sulphur called macronutrients?
Ans. As these are needed in large amounts app. one to ten mg per gram of the dry matter.
INTEXT QUESTIONS 9.3
1. State any two metabolic processes for which mineral nutrition is required.
Ans. (i) Turgidity of the cells. and
(ii) enzyme activity.
2. Which element is provided by NO₂and NH₄ when taken up by plants?
Ans. Nitrogen.
3. State any two functions of Ca²⁺ in plants.
Ans. Two functions of Ca²⁺ in plants are following:
(a) Development of root and shoot apex.
(b) Formation of middle lamella in plant cells.
INTEXT QUESTIONS 9.4
1. What is meant by ‘passive absorption’ of minerals by plants?
Ans. It is the absorption of minerals with- out expenditure of the energy.
2. Name the minerals whose deficiency affects normal cell division.
Ans. (i) Mo.
(ii) S.
(iii) K.
(iv) N.
3. “Deficiency of K, Ca and Mg causes necrosis of leaves”. What does this statement mean?
Ans. It means “the deficiency causes the death of the tissues of leaves”.
INTEXT QUESTIONS 9.5
1. Give one point of difference between autotrophic and heterotrophic nutrition.
Ans. Difference Between Autotrophic and Heterotrophic Nutrition:
| Autotrophic Nutrition | Heterotrophic Nutrition |
| They synthesise their own food like green plants. | They depend on others for their food, e.g. parasitic plants. |
2. Name a plant which exhibits parasitic mode of nutrition.
Ans. The dodder plant (Cuscuta reflexa).
3. Why does pitcher plant eat insects when it is capable of carrying out photosynthesis?
Ans. Since this grows in a nitrogen deficient habitat.
TERMINAL EXERCISES
1. Which element can be obtained from both mineral and non-mineral sources.
Ans. Carbon.
2. Deficiency of which essential element causes yellowing of leaves in certain plants and why?
Ans. Magnesium. It is an essential element and its deficiency causes yellowing of leaves. The green pigment is chlorophyll and Mg is essential for its formation.
3. Why is magnesium included among essential elements?
Ans. It is required by the plant in larger amounts and is included in the essential elements category since it is necessary for formation of chlorophyll. Its deficiencies lead to the yellowing of the leaves.
4. What are the criteria of essentiality of elements?
Ans. See the following criteria:
(a) An essential element is absolutely essential for normal growth as well as the reproduction of plants.
(b) Requirement of an element is very specific. One cannot be replaced by the another element.
(c) Element is directly involved in nutrition of the plant.
5. Differentiate between micro and macro nutrients.
Ans. Difference Between Micronutrients and Macronutrients:
| Mironutrients (Microelements) | Macronutrients (Macroelements) |
| 1. e.g., Manganese, Iron, Copper, Molybdenum, Zinc and Chlorine. | e.g., Carbon, Hydrogen, Oxygen, Phosphorus, Potassium, Calcium and Nitrogen, Sulphur and Magnesium. |
| 2. Needed in minute quantities app. 0.1 mg per gram of dry matter of less than it. These are known as the trace elements. | Needed in relatively large quantities approximately to 10 milligram per gram of dry matter. |
6. Why do biologists grow plants by hydroponics technique?
Ans. Hydrophonics Technique: It is needed to know the essentiality of an element for normal growth and how much quantity is necessary. The plants are grown in culture or nutrient mediums in a tank and it has been applied in tomatoes and lettuce. There is no need of soil. It is also called water culture.
A culture solution contains all essential nutrients except one whole importance can be detected. The plant that is grown in culture solution is now compared to the other growing with all essential elements; say control experiment.
7. Explain the uptake of mineral nutrients by the plants.
Ans. Mineral Uptake by Plants: The minerals are taken up by roots through active absorption and passive absorption.
(i) Passive absorption: It does not need energy. It occurs rapidly. Ions are absorbed into apoplast.
(ii) Active absorption: It needs metabolic energy. It occurs slowly. The ions are absorbed into inner space, symplast of cells.
8. Give the deficiency symptoms of nitrogen, phosphorus and potassium.
Ans.
| Element | Deficiency symptom |
| 1. Nitrogen | Stunted growth, older leaves become yellow (chlorosis); delay in flowering etc. |
| 2. Phosphorus | Stunted plant growth, premature fall of leaves, Inhibition of cell division, etc. |
| 3. Potassium | Chlorosis, Necrosis, Inhibition of cell division, Retarded growth of a plant. Premature fall of the leaves of plants. |
9. Differentiate between the different modes of heterotrophic nutrition in plants.
Ans. Heterotrophic plants: These are broadly classified into three main groups:
(i) saprophytes.
(ii) parasites. and
(iii) insectivorous plants.
Differences between Saprophytes, Parasites and Insectivorous Plants:
| S. No. | Saprophyte Plants | Saprophytic Plant | Insectivorous Plants |
| 1 | Sapros = rotten; phyton = plant. | Para = besides and sites means food. | Insectivore = eats the insects. |
| 2 | Grow and live on dead, decaying organic matter, animal and plant remains. | The parasites live and grow on hosts and get nourishment for its body and cause physical harm to host plant. | They tap and eat insects to supplement mineral deficiency. |
| 3 | Examples are Monotropa; (It occurs in Khasi hills, Meghalaya in India; others are Neottia, bacteria, fungi. Fig. 9.3. Monotropa. | Examples are Cuscuta, Rafflesia, Orobanchae, Loranthus and Santalum album as well as Viscum. Fig. 9.4. (A-B) Orobanche (Total root parasite) growing in brinjal roots. | Examples are Nepenthes (pitcher plant), Drosera, Dionea and Aldrovanda as well as Utricularia (Bladderwort). Fig. 9.5. Drosera (Sundew plant). |
10. Write notes on:
(i) Aeroponics.
Ans. Aeroponics: It refers “to the owing of plants with roots in nutrient mist environment or in air but without use of soil.” The rooted plants are exposed in air. It has been used in Citrus plants.
(ii) Insectivorous plants.
Ans. Insectivorous plants: These plants trap insects for their nutrition, e.g. Drosera and pitcher plant.
(iii) Active absorption of minerals by plants.
Ans. Active Absorption of Minerals by Plants: It occurs against concentration gradient. Metabolic energy (ATP) is used in order to perform active absorption. It occurs through the agency of specific carriers present on the surface of plasma membrane. They may be organic molecules. Pinosomes also act as carriers.
